Establishment of a novel protocol for assessing the severity of subarachnoid hemorrhage in circle Willis perforation mouse model.

The Circle of Willis perforation (cWp) mouse model is a key tool in subarachnoid hemorrhage (SAH) research; however, inconsistent bleeding volumes can challenge experimental reliability. To address this issue, we introduced the ROB Scoring System, a novel protocol integrating Rotarod Tests (RT), Open-field Tests (OT) video analysis, and daily Body Weight Loss (BWL) monitoring to precisely categorize SAH severity. Forty C57BL/6 mice underwent cWp SAH induction, categorized by ROB into severity subgroups (severe, moderate, mild). Validation compared ROB trends in subgroups, and ROB outcomes with autopsy results on postoperative days three and seven for acute and sub-acute evaluations. Mortality rates were analyzed via the survival log-rank test, revealing a significant difference among SAH subgroups (P < 0.05). Strong correlations between ROB grades and autopsy findings underscored its precision. Notably, the severe group exhibited 100% mortality within 4 days post SAH onset. Single parameters (RT, OT, BWL) were insufficient for distinguishing SAH severity levels. The ROB score represents a significant advancement, offering an objective method for precise categorization and addressing inherent bleeding variations in the cWp SAH model. This standardized protocol enhances the reliability and effectiveness of the SAH translational research, providing a valuable tool for future investigations into this critical area.

Influence of circle of Willis modeling on hemodynamic parameters in anterior communicating artery aneurysms and recommendations for model selection.

Computational fluid dynamics (CFD) has been utilized to calculate hemodynamic parameters in anterior communicating artery aneurysm (AComA), which is located at a junction between left and right A1 and A2 segments. However, complete or half circle of Willis (CoW) models are used indiscriminately. This study aims to suggest recommendations for determining suitable CoW model. Five patient-specific CoW models with AComA were used, and each model was divided into complete, left-half, and right-half models. After validating the CFD using a flow experiment, the hemodynamic parameters and flow patterns in five AComAs were compared. In four out of five cases, inflow from one A1 side had a dominant influence on the AComA, while both left and right A1 sides affected the AComA in the remaining case. Also, the average difference in time-averaged wall shear stress between the complete and half models for four cases was 4.6%, but it was 62% in the other case. The differences in the vascular resistances of left and right A1 and A2 segments greatly influenced the flow patterns in the AComA. These results may help to enhance clinicians' understanding of blood flow in the brain, leading to improvements in diagnosis and treatment of cerebral aneurysms.

Exploring the anatomical configurations of the cerebral arteries in a cohort of South African patients.

The cerebral arteries, specifically the anterior cerebral artery (ACA) and posterior cerebral artery (PCA), work together with the smaller calibre arteries to provide effective communication between the anterior and posterior circuits of the brain via the circle of Willis (CoW). Morphologic variations of the cerebral arteries and the CoW may alter blood flow to the brain, resulting in intracranial vascular disorders associated with stroke, and aneurysms. This study aimed to document the morphology of the cerebral arteries and the CoW in the South African population. Two hundred and thirty-nine computed tomography angiography scans were assessed. Cerebral arteries and CoW normal morphology and variations were classified as complete, absent, or hypoplastic. The ACA A1 was absent in 4.91%, hypoplastic in 30.40%, fenestrated in 1.06%, and typical in 63.6%. The ACA A2 was absent in 0.42%, hypoplastic in 26.28%, and typical in 69.44%. We found triple ACA A2 in 2.98%, azygos in 1.28% and fenestrated in 1.28%. The middle cerebral artery (MCA) was hypoplastic in 7.35% and typical in 92.64%. The PCA was hypoplastic in 28.74% and typical in 71.25%. Knowledge of the configuration of the CoW plays a significant role in guiding therapeutic decision-making in treating various neurovascular pathologies.

Trend of cerebral aneurysms over the past two centuries: need for early screening.

OBJECTIVE: Cerebral aneurysms (CAs) are linked to variations in the cerebral basal arterial network (CBAN). This study aimed to find the optimal age for screening to detect brain arterial variations and predict aneurysms before rupture. DESIGN: An observational, quantitative and retrospective research. SETTING: The study analysed 1127 cases of CAs published from 1761 to 1938. Additionally, CT angiography images of 173-patients at the Royal Adelaide Hospital (RAH), South Australia between 2011 and 2019 were examined for the presence and the location of aneurysms in CBAN. PARTICIPANTS: The data were collected from patients at RAH and 407 published sources, including males and females across the entire age range, up to 100 years old. OUTCOME MEASURES AND RESULTS: Data, CAs cases, from 1761 to 1938 included (526 males, 573 females and 28 unknown sexes). The age of these patients varied from 18 months to 89 years (mean age=42, SD=18). Approximately 11.5% of the CAs occurred in patients aged <20 years. Among the 1078 aneurysms whose location was reported, 76% were located in the internal carotid (IC), middle cerebral (MC) and anterior communicating artery complex (AcomAC) regions, while the remaining 24% were in the vertebrobasilar region. Among 173 patients from RAH aged between 18 and 100 years (male=83 and female=90, mean age=60, SD=16), 94% of the CAs were found in the IC, MC and AcomAC regions. The pattern of aneurysm occurrence, as indicated by values at the 25th, 50th and 75th percentiles, along with the minimum and maximum patient ages, has remained consistent from 1761 to 2019. CONCLUSION: The distribution pattern of CAs in relation to sex, age and locations in the CBAN, remained steady over the last 260 years resulting in risk of strokes early in life. Therefore, early screening for CBAN segment variations is advised for stroke prevention if possible.

Chemotherapy-associated hemorrhagic posterior reversible encephalopathy syndrome (PRES) with considerations for circle of Willis variants on cerebral blood flow and autoregulation: A case report.

RATIONALE: Hodgkin lymphoma, a lymphatic system cancer, is treated by chemotherapy, radiation therapy, and hematopoietic stem cell transplantation. Posterior reversible encephalopathy syndrome (PRES) is a rare neurotoxic effect associated with several drugs and systemic conditions. This case study emphasizes the potential risks of intensive chemotherapy regimens and postulates the impact of the circle of Willis variants on the heterogeneity of hemispheric lesions in PRES. PATIENT CONCERNS: A 42-year-old woman diagnosed with stage IIA nodular sclerosing Hodgkin lymphoma and chronic thrombocytopenia presented after 6 years of initial diagnosis and 4 years post-haploidentical transplant. She underwent planned chemotherapy with ifosfamide, carboplatin, and etoposide. DIAGNOSES: She developed an alteration in her mental status. A computerized tomography scan and angiogram of the head and neck revealed findings consistent with PRES and a left fetal-type posterior cerebral artery with an aplastic A1 segment of the left anterior cerebral artery. One hour later she was found comatose with clinical sequelae of an uncal herniation. INTERVENTIONS: Subsequent events led to emergent intubation, and administration of 23.4% hypertonic saline. A repeat computerized tomography scan showed a right intraparenchymal hemorrhage with fluid-fluid levels measuring up to 4.7 cm, bilateral subarachnoid hemorrhage, right uncal herniation, and 15 mm of leftward midline shift. She emergently underwent a right decompressive hemi-craniectomy. OUTCOMES: An magnetic resonance imaging of the brain demonstrated bilateral cytotoxic edema involving the parieto-occipital lobes. Despite interventions, the patient's neurological condition deteriorated, leading to a declaration of brain death on the 8th day. LESSONS: This case underscores the importance of recognizing the severe neurological complications, including PRES, associated with chemotherapeutic treatments in Hodgkin lymphoma. PRES may also be exacerbated by coagulopathies such as thrombocytopenia in this case. The circle of Willis variants may influence cerebral blood flow, autoregulation, and other factors of hemodynamics, leading to increased susceptibility to both radiographic lesion burden and the worst clinical outcomes.

Neurovascular description in the South American plains vizcacha, Lagostomus maximus (Chinchilloidea, Caviomorpha). A study involving evolutionarily related species of Caviomorpha and Muroidea.

Oxygenated blood is required for the adequate metabolic activity of the brain. This is supplied by the circle of Willis (CoW) and the vertebrobasilar and carotid systems. The CoW ensures blood flow in case of arterial stenosis or occlusion. Different animal models have been explored for the CoW morphological and functional study. This work aims to characterize the vascular architecture of the CoW of the plains vizcacha, Lagostomus maximus (Suborder: Hystricomorpha), and to compare it with evolutionarily related species of Caviomorpha and Muroidea. The blood supply in adult plains vizcachas was studied using latex cerebrovascular casts and angiography. A caudo-rostral flow direction was determined, beginning in the spinal and vertebral arteries and converging in the basilar artery which bifurcates in the carotid-basilar communication in the caudal communicating arteries. In the first third of its course, the caudal cerebral arteries project laterally, and the middle and rostral cerebral arteries bifurcate from their rostral terminal segment, supplying the temporo-parietal and frontal cortex. The CoW architecture is mainly conserved between rodent species. Likewise, the small neurovascular variations observed could be considered phylogenetic morphological variations more than evolutionary adaptations. The absence of the rostral communicating artery that generates the rostral open architecture of the CoW in the vizcacha as in the other analyzed species, supports the need for a revision of the CoW classical function as a security system. Finally, this work supports the importance of expanding our understanding of brain anatomy among species, which may contribute to a better understanding of functional neuroanatomy.

Development of the Circle of Willis Score (COWS) to help guide decision making during acute tandem occlusion treatment: Preliminary analysis.

BACKGROUND: Acute tandem occlusions (TOs) are challenging to treat. Although acute carotid stenting of the proximal lesion is well tolerated, there are certain situations when the practitioner may be wary of acute stenting (bleeding concerns). OBJECTIVE: The purpose of this study was to retrospectively study patients with tandem occlusions who had re-occlusion of the extracranial ICA and develop a Circle of Willis Score (COWS) to help predict which patients could forego acute stenting. METHODS: This is a retrospective review of TO patients with a persistent proximal occlusion following intervention (either expected or unexpected). Pre intervention CTA and intraoperative DSA were reviewed, and each patient was assigned a score 2 (complete COW), 1a (patent A1-Acomm-A1), 1p (patent Pcomm), or 0 (incomplete COW). Findings from the DSA took precedence over the CTA. Two cohorts were created, the complete COW cohort (COWS 2) versus the incomplete COW cohort (COWS 1a,1p, or 0). Angiographic outcomes were assessed using the mTICI score (2b-3) and clinical outcomes were assessed using discharge mRS (good outcome mRS 0-3). RESULTS: Of 68 TO cases, 12 had persistent proximal occlusions. There were 5/12 (42 %) patients in the complete COW cohort, and 7/12 (58 %) in the incomplete COW cohort (5/12 with scores of 1a/1p and 2/12 with a score of 0). In the complete COW cohort, there were 2 ICA-ICA and 3 ICA-MCA occlusions. In the incomplete COW cohort, there was one ICA-ICA occlusion and 6 ICA-MCA occlusions. LKW-puncture was shorter in the complete COW cohort (208 min vs. 464 min, p = 0.16). Successful reperfusion was higher in the complete COW cohort (100 % vs. 71 %). There was a trend toward better clinical outcomes in the complete COW cohort (80 % vs 29 %, p = 0.079). CONCLUSION: The COWS is a simple score that may help predict a successful clinical outcome without proximal revascularization when concerned about performing an acute carotid stent during TO treatment. Evaluation in larger TO cohort is warranted.

Hemodynamic characteristics and mechanism for intracranial aneurysms initiation with the circle of Willis anomaly.

Clinically, circle of Willis (CoW) is prone to anomaly and is also the predominant incidence site of intracranial aneurysms (IAs). This study aims to investigate the hemodynamic characteristics of CoW anomaly, and ascertain the mechanism of IAs initiation from the perspective of hemodynamics. Thus, the flow of IAs and pre-IAs were analyzed for one type of cerebral artery anomaly, that is, anterior cerebral artery A1 segment (ACA-A1) unilateral absence. Three patient geometrical models with IAs were selected from Emory University Open Source Data Center. IAs were virtually removed from the geometrical models to simulate the pre-IAs geometry. For calculation methods, a one-dimensional (1-D) solver and a three-dimensional (3-D) solver were combined to obtain the hemodynamic characteristics. The numerical simulation revealed that the average flow of Anterior Communicating Artery (ACoA) is almost zero when CoW is complete. In contrast, ACoA flow increases significantly in the case of ACA-A1 unilateral absence. For per-IAs geometry, the jet flow is found at the bifurcation between contralateral ACA-A1 and ACoA, which exhibits characteristics of high Wall Shear Stress (WSS) and high wall pressure in the impact region. It triggers the initiation of IAs from the perspective of hemodynamics. The vascular anomaly that leads to jet flow should be considered as a risk factor for IAs initiation.

Anatomical differences of intracranial arteries according to sex: a systematic review and meta-analysis.

BACKGROUND AND PURPOSE: Intracranial aneurysms are more common in women than in men. Some anatomical variants of the circle of Willis (CoW) are associated with a higher risk of developing intracranial aneurysms. We hypothesized that variations of the CoW are sex dependent which may partly explain why intracranial aneurysms are more common in women. We systematically reviewed and meta-analyzed the literature to compare the presence of anatomical variations of the CoW between women and men in the general population. MATERIAL AND METHODS: A systematic search in Pubmed and EMBASE using predefined criteria, following the PRISMA guidelines was performed. The presence of different CoW anatomical variants and a complete CoW was compared between women and men using an inverse variance weighted random effects meta-analysis to calculate relative risks (RR) with 95% confidence intervals (95% CIs). RESULTS: Fourteen studies were included reporting on 5478 healthy participants (2511 women, 2967 men). Bilateral fetal type posterior cerebral arteries (RR 2.79; 95%CI 1.65-4.72, I2=0%), and a complete CoW (RR 1.24, 95%CI 1.13-1.36; I2=0%) were more prevalent in women than in men. The variants absence or hypoplasia of one of the anterior cerebral arteries (RR 0.58, 95%CI 0.38-0.88, I2=57%) and hypoplasia or absence of both posterior communicating arteries (RR 0.79, 95%CI 0.71-0.87, I2=0%) were more prevalent in men. CONCLUSIONS: Several anatomical variations of the CoW are sex dependent, with some variants being more common in women while others in men. Future research should assess how these sex-specific CoW variants relate to the sex-specific occurrence of intracranial aneurysms.

Anatomical variations in the cerebral arterial circle of the Saimaa (Pusa hispida saimensis) and Baltic ringed seals (Pusa hispida botnica).

The intracranial arterial vascularization of the Saimaa ringed seals (Pusa hispida saimensis; Nordquist, 1899) and Baltic ringed seals (Pusa hispida botnica; Gmelin, 1788) disclosed patterns of anatomical architecture comparable to that of other pinniped species. Arterial silicone casts on skull scaffolds, and magnetic resonance imaging (MRI) showed that the besides joining the caudal communicating arteries upon entering the cerebral arterial circle, the bilateral internal carotid arteries bifurcated as laterally oriented rostral choroidal arteries and rostral cerebral arteries. The latter arteries almost immediately gave off the laterally oriented middle cerebral arteries. Numerous individual variations were evident in differences in the exact branching sites of bilateral vessels or the size or number of arterial branches. Two Saimaa ringed seals had only a tiny foramen for the left internal carotid artery to enter the intracranial space, and the intracranial part of this vessel was short. It did not reach the cerebral arterial circle. The intracranial part of the right internal carotid artery is bifurcated and also supplied the left side of the cerebral arterial circle. Both specimens had aplasia of the left rostral cerebral artery. The intracranial arterial arrangement of Saimaa and Baltic ringed seals reflects the arterial architecture of this body region in terrestrial mammals with little evidence for aquatic adaptations or changes related to thermoregulation.

The Importance of the Circle of Willis in Carotid Interventions Outcomes: A Real-Life Study.

BACKGROUND: The main objective of this study is to evaluate and compare the outcomes regarding operative mortality rate, ipsilateral stroke, and overall survival rate among patients with internal carotid artery stenosis submitted to carotid endarterectomy (CEA) or stenting regarding the completeness of circle of Willis (CoW). METHODS: Prospective, consecutive cohort study of patients submitted to carotid interventions (CEA and carotid stenting: CAS) for internal carotid artery stenosis diagnosis evaluated according complete or incomplete CoW. The patients were divided into 2 groups: group I, the patients with complete CoW and group II, the patients with incomplete CoW, with the disruption of anterior and/or ipsilateral posterior circulation, regarding the ipsilateral significant carotid stenosis. RESULTS: Overall, 98 patients submitted to carotid intervention were evaluated. Two groups of patients were identified: group CoW complete with 54 patients and group CoW incomplete with 44 patients. Regarding the type of intervention, the prevalence of CAS in CoW complete group and CoW incomplete group were statistically similar (54.1% vs. 55.1%, P = 0.22). Notwithstanding, CEA was also statistically similar in CoW incomplete group and CoW complete group (44.2% vs. 45.9%, P = 0.22). The perioperative mortality rate was 2% in total cohort (2 patients), with no differences among CoW complete and incomplete groups (3.7% vs. 0%, P = 0.50, respectively). Furthermore, the incidence of postoperative stroke was 3.1% (asymptomatic 2%, symptomatic 1.1%), with no differences among CoW complete and incomplete groups (3.7% vs. 2.3%, P = 0.68, respectively). A univariate and multivariate linear regression showed that among the factors evaluated, only chronic kidney failure was related with hazard ratio = 1.89, P = 0.003, confidence interval 1.058-2.850. CONCLUSIONS: The completeness of the CoW, independently of the type of carotid intervention (CEA and CAS), did not interfere in the results regarding postoperative outcomes for stroke and death. Chronic kidney disease was associated to increased risk of perioperative stroke.

Anatomical Variations and Anomalies of the Anterior Communicating Artery Complex.

BACKGROUND: Intracranial arteries have a high rate of variation, but a clear schematic overview is lacking. In this pictorial review we classify and depict all variations and anomalies within the anterior communicating artery complex. METHODS: PubMed was searched with the terms "Anterior Communicating Artery" AND "Variations" OR "Anomalies." Articles were selected based on their description of variants. Cross-referencing was used to broaden the range of variations. Surgical view during pterional craniotomy and transsylvian approach was used as a baseline for schematic drawings of the variations. RESULTS: A total of 42 variants were identified, schematically drawn and classified into A1-A2 segment, anterior communicating artery, and the recurrent artery of Heubner. CONCLUSIONS: The anterior communicating artery complex consists of the anterior cerebral artery, anterior communicating artery and the recurrent artery of Heubner. An overview of these variations may be helpful in distinguishing pathology from anatomical variations, assist neurosurgeons during clipping of cerebral aneurysms, and support interventional radiologists during endovascular treatments. This article summarizes the current knowledge of anatomical variations within the anterior communicating artery complex, their prevalence and clinical relevance. A total of 42 variants were identified and schematically depicted. We encourage all who diagnose, treat, and study the anterior communicating artery complex to use this overview for a uniform and better understanding of its anatomy.

High resolution simulation of basilar artery infarct and flow within the circle of Willis.

On a global scale, cerebro- and cardiovascular diseases have long been one of the leading causes of death and disability and their prevalence appears to be increasing in recent times. Understanding potential biomarkers and risk factors will help to identify individuals potentially at risk of suffering an ischemic stroke. However, the widely variable construction of the cerebral vasculature makes it difficult to provide a specific assessment without the knowledge of a patient's physiology. In this paper we use the 3D blood flow simulator HemeLB to study flow within three common structural variations of the circle of Willis during and in the moments after a blockage of the basilar artery. This tool, based on the lattice Boltzmann method, allows the 3D flow entering the basilar artery to be finely controlled to replicate the cessation of blood feeding this particular vessel-we demonstrate this with several examples including a sudden halt to flow and a gradual loss of flow over three heartbeat cycles. In this work we start with an individualised 3D representation of a full circle of Willis and then construct two further domains by removing the left or right posterior communicating arteries from this geometry. Our results indicate how, and how quickly, the circle of Willis is able to redistribute flow following such a stroke. Due to the choice of infarct, the greatest reduction in flow was observed in the posterior cerebral arteries where flow was reduced by up to 70% in some cases. The high resolution domains used in this study permit the velocity magnitude and wall shear stress to be analysed at key points during and following the stroke. The model we present here indicates how personalised vessels are required to provide the best insight into stroke risk for a given individual.

Circle of Willis Configuration and Thrombus Localization Impact on Ischemic Stroke Patient Outcomes: A Systematic Review.

Background and Objectives: The published literature highlights the fact that the integrity of the Circle of Willis has a direct impact on stroke outcome, especially in cases of distal internal carotid T occlusion. The aim of this study was to review the available data on the Circle of Willis configuration and thrombus location impact on patient outcome in cases of ischemic stroke. Materials and Methods: A systematic search according to PRISMA guidelines was performed in PubMed, Cochrane, and EMBASE databases to identify studies investigating the influence of Circle of Willis variants on ischemic stroke outcomes published up to March 2023. The manuscripts were reviewed by three researchers separately and scored on the quality of the research using the MINORS criteria. Results: After screening 157 manuscripts, 11 studies (n = 4643) were included. Circle of Willis integrity plays a vital role in stroke outcome, especially when T-form occlusions are present. Despite this, in the event of M1 occlusion Circle of Willis configuration does not play an important role. In cases of distal internal carotid artery occlusion, the presence of a fully developed contralateral A1 segment and anterior communicating artery is essential for a favorable stroke outcome. Conclusions: The preserved integrity of the Circle of Willis has great significance for collateral flow in the event of ischemic stroke and helps patients to achieve more favorable outcomes, as it determines the affected brain territory. The clinical outcome of the ischemic stroke appears to be significantly better if only one artery territory is affected, compared to two or more.

Hemorragia Intracerebral Imprevisible en un Hombre Joven: La Importancia de la Tomografía computarizada craneal post-mortem / Unpredictable Intracerebral Hemorrhage in a Young Male: The Importance of Post-Mortem Cranial Computed Tomography

La muerte súbita es aquella que ocurre dentro de las 24 horas posteriores al inicio de los síntomas y se caracteriza por ser clínicamente inexplicable, inesperada y repentina. Debido a la naturaleza de la muerte súbita, no es posible llegar a un diagnóstico preciso sin una autopsia. En esta comunicación breve, evaluaremos el caso de un empleado de crucero de 33 años, sin historial médico/farmacológico previo, el cual falleció súbitamente mientras reposaba en su camarote. Debido a las sospechas iniciales de una posible muerte causada por una sobredosis de cocaína, se le realizó un panel toxicológico abarcador el cual resultó negativo. Empero, una tomografía computarizada (TC) craneal sin contraste revirtió la hipótesis inicial y la autopsia neuropatológica -sorpresivamente- confirmó que la verdadera causa de muerte fue la ruptura de un aneurisma sacular desconocido en el polígono de Willis.

Sudden death occurs within 24 hours after the onset of symptoms and is characterized by being clinically inexplicable, sudden, and unexpected. Due to the nature of sudden death, it is not possible an accurate diagnosis without performing an autopsy. In this brief communication, we will evaluate the case of a 33-year-old cruise employee, with no prior medical/pharmacological history, who suddenly died while resting in his cabin. Due to initial suspicions of a possible cocaine overdose death, a comprehensive toxicology panel was performed, although yielding a negative result. A cranial computed tomography without contrast reversed the initial hypothesis and the neuropathological autopsy -surprisingly- confirmed that the true cause of death was the rupture of an unknown saccular aneurysm in the Circle of Willis.

Comparison of bone subtraction CT angiography with standard CT angiography for evaluating circle of Willis in normal dogs.

BACKGROUND: Bone subtraction computed tomography angiography (BSCTA) is a useful alternative technique for improving visualization of vessels surrounded by skull bone. However, no studies have compared computed tomography angiography (CTA) and BSCTA for improving the visibility of canine cerebral blood vessels. OBJECTIVES: To evaluate the potential benefit of BSCTA for better delineation of brain arteries of the circle of Willis (CoW) in dogs by comparing BSCTA with non-subtraction computed tomography angiography (NSCTA). METHODS: Brain CTA was performed for nine healthy beagle dogs using a bolus tracking method with saline flushing. A total dose of 600 mgI/kg of contrast agent with an iodine content of 370 mgI/mL was injected at a rate of 4 ml/s. Bone removal was achieved automatically by subtracting non-enhanced computed tomography (CT) data from contrast CT data. Five main intracranial arteries of the CoW were analyzed and graded on a scale of five for qualitative evaluation. RESULTS: Scores of basilar artery, middle cerebral artery, and rostral cerebral artery in the BSCTA group were significantly higher than those in the NSCTA group (p = 0.001, p = 0.020, and p < 0.0001, respectively). Scores of rostral cerebellar artery (RcA) and caudal cerebral artery (CCA) did not differ significantly between the two groups. However, scores of RcA and CCA in the BSCTA group were higher than those in the NSCTA group. CONCLUSIONS: BSCTA improved visualization of intracranial arteries of the CoW with close contact to bone. Thus, it should be recommended as a routine scan method in dogs suspected of having brain vessel disease.

Evidence and Mechanisms for Embolic Stroke in Contralateral Hemispheres From Carotid Artery Sources.

BACKGROUND: Disambiguation of embolus pathogenesis in embolic strokes is often a clinical challenge. One common source of embolic stroke is the carotid arteries, with emboli originating due to plaque buildup or perioperatively during revascularization procedures. Although it is commonly thought that thromboemboli from carotid sources travel to cerebral arteries ipsilaterally, there are existing reports of contralateral embolic events that complicate embolus source destination relationship for carotid sources. Here, we hypothesize that emboli from carotid sources can travel to contralateral hemispheres and that embolus interactions with collateral hemodynamics in the circle of Willis influence this process. METHODS AND RESULTS: We use a patient-specific computational embolus-hemodynamics interaction model developed in prior works to conduct an in silico experiment spanning 4 patient vascular models, 6 circle of Willis anastomosis variants, and 3 different thromboembolus sizes released from left and right carotid artery sites. This led to a total of 144 different experiments, estimating trajectories and distribution of approximately 1.728 million embolus samples. Across all cases considered, emboli from left and right carotid sources showed nonzero contralateral transport (P value <-0.05). Contralateral movement revealed a size dependence, with smaller emboli traveling more contralaterally. Detailed analysis of embolus dynamics revealed that collateral flow routes in the circle of Willis played a role in routing emboli, and transhemispheric movement occurred through the anterior and posterior communicating arteries in the circle of Willis. CONCLUSIONS: We generated quantitative data demonstrating the complex dynamics of finite size thromboembolus particles as they interact with pulsatile arterial hemodynamics and traverse the vascular network of the circle of Willis. This leads to a nonintuitive source-destination relationship for emboli originating from carotid artery sites, and emboli from carotid sources can potentially travel to cerebral arteries on contralateral hemispheres.

Using deep learning for an automatic detection and classification of the vascular bifurcations along the Circle of Willis.

Most of the intracranial aneurysms (ICA) occur on a specific portion of the cerebral vascular tree named the Circle of Willis (CoW). More particularly, they mainly arise onto fifteen of the major arterial bifurcations constituting this circular structure. Hence, for an efficient and timely diagnosis it is critical to develop some methods being able to accurately recognize each Bifurcation of Interest (BoI). Indeed, an automatic extraction of the bifurcations presenting the higher risk of developing an ICA would offer the neuroradiologists a quick glance at the most alarming areas. Due to the recent efforts on Artificial Intelligence, Deep Learning turned out to be the best performing technology for many pattern recognition tasks. Moreover, various methods have been particularly designed for medical image analysis purposes. This study intends to assist the neuroradiologists to promptly locate any bifurcation presenting a high risk of ICA occurrence. It can be seen as a Computer Aided Diagnosis scheme, where the Artificial Intelligence facilitates the access to the regions of interest within the MRI. In this work, we propose a method for a fully automatic detection and recognition of the bifurcations of interest forming the Circle of Willis. Several neural networks architectures have been tested, and we thoroughly evaluate the bifurcation recognition rate.

Incompleteness of the Circle of Willis and progression of white matter hyperintensities of presumed vascular origin. A longitudinal prospective study in community-dwelling older adults.

BACKGROUND: Evidence on the association between anatomical variants of the circle of Willis (CoW) and severity of white matter hyperintensities (WMH) of presumed vascular origin is inconclusive, and no study has evaluated the role of incompleteness of CoW on WMH progression in the follow-up. This study aims to assess the impact of incomplete configurations of the CoW on WMH progression in community-dwelling older adults. METHODS: Following a prospective longitudinal study design, individuals aged ≥60 years enrolled in the Atahualpa Project Cohort from 2012 to 2019 were invited to receive baseline brain MRI and MRA of intracranial vessels, and those who also had brain MRIs at the end of the study (May 2021) were included in the analysis. Poisson regression models, adjusted for demographics and cardiovascular risk factors, were fitted to assess the incidence rate ratio (IRR) of WMH progression according to incompleteness of CoW. RESULTS: This study included 254 individuals (mean age: 65.4±5.9 years; 55% women). An incomplete CoW was detected in 99 (39%) subjects. Follow-up MRIs showed WMH progression in 103 (41%) individuals after a median follow-up of 6.5±1.4 years. WMH progression was observed in 58/155 subjects with complete and in 45/99 with incomplete CoW (37% versus 45%; p=0.203). There was no association between incomplete CoW and WMH progression in a multivariate Poisson regression model (IRR: 1.21; 95% C.I.: 0.81 - 1.82). CONCLUSIONS: Study results show that incompleteness of CoW is not involved in WMH progression.